1. Introduction
Biogas, an alternative renewable energy, can be produced from various organic containing sources such as animal manure, agricultural and industrial wastewaters, garbage and agriculture-residues by anaerobic process. The use of biogas has been increased for many applications such as boilersand internal combustion engines. The presence of a trace amount of hydrogen sulfide (H2S) in the biogas is harmful to human health and cause significant corrosive damage to the equipments or machines contacting the biogas. The previous reports revealed that hydrogen sulfide concentration above 10 ppm can affect human health, while levels exceed 750 ppm can immediately cause unconsciousness or death [1]. Physical and chemical processes for hydrogen sulfide removal have many disadvantages regarding its high costs, and secondary waste production. The biotrickling filter, which is biological treatment process, is the one of alternative solution for these problems. The microorganisms used in these bioprocesses are able to convert hydrogen sulfide into elemental sulfur and sulfate. Chemoautotrophic bacteria are microorganisms that obtain the carbon sources for growth from carbon dioxide (CO2) and obtain energy from the oxidation of inorganic compounds as hydrogen sulfide. Applying these microorganisms in the biotrickling filter can eliminate both hydrogen sulfide and carbon dioxideat the same time[2]. Potential sources of chemoautotrophic bacteria were selected for screening and characterizing pure bacterial strains capable of hydrogen sulfide and carbon dioxide removal in biogas stream. Optimum buffer concentration (phosphate buffer) and thiosulfate concentrations were evaluated for microbial growth and sulfuroxidation activitybefore applying the pure strain into biotrickling filtersystem.